Melanoma and Breast Cancer: A New Warning

If you've had breast cancer or melanoma (the deadliest form of skin cancer), be aware that having either one raises the odds of developing the other, according to a recent study published in the Irish Journal of Medical Science.

While earlier studies have noted an association between the two malignancies, this is the first time researchers have explicitly advised doctors to monitor breast cancer patients for signs of melanoma, and vice versa. They also recommend that melanoma patients with a family history of breast cancer have regular mammographies or breast MRIs (magnetic resonance imaging).

What the Numbers Say

Investigators led by photobiologist Gillian M. Murphy, MD, of the Beaumont Hospital in Dublin, and a member of The Skin Cancer Foundation's International Advisory Council, examined the 6,788 cases of melanoma and 27,597 cases of breast carcinoma between 1994 and 2007 documented in Ireland's National Cancer Registry. They mathematically determined that if there was no statistically significant relationship between the two, 30-35 patients could be expected to have both malignancies. Instead, there were 127. "In general, patients with melanoma or other skin cancers are always at higher risk of developing other malignancies," Dr. Murphy commented. "But this is about a fourfold increase, which raises the possibility of a genetic predisposition linking the two cancers."

The study corroborates the findings of journals such as Annals of Oncology and Breast Cancer Research and Treatment, which reported that breast cancer patients have between 1.4 and 2.7 times the risk of developing melanoma. And the danger is reciprocal: The International Journal of Cancer noted that female melanoma patients have a 1.4 times greater chance of developing breast cancer.

According to Dr. Murphy, "Holistic treatment should include not only melanoma management, but also education and appropriate investigation regarding other co-morbidities (related illnesses), including breast cancer, as well as vitamin D supplementation where relevant." Murphy and her coauthors recommend that all melanoma patients inform their physicians of any history of cancer. Additionally, female melanoma patients should have routine breast exams and, if there's any family history of breast carcinoma, annual mammographies (if over age 40), or regular breast MRIs (if under 40): Patients under 40 are at higher risk than older patients for both development and recurrence of the disease.

Is It in the Genes?

It's unclear just how great a role genes play in the development of breast cancer and melanoma. Research suggests that mutations in CDKN2A, a gene that indicates high risk of developing melanoma, also puts carriers at up to 3.8 times greater risk of breast cancer. Similarly, mutations in the gene for breast cancer susceptibility, BRCA2, increase carriers' risk of melanoma by as much as 2.58 times. However, as Dr. Murphy observed, "Only a minority of melanoma cases have identifiable genetic mutations." Just 5 to 10 percent of melanomas occur in families with multiple cases of the disease, and in only 20-40 percent of these families is there a mutation in CDKN2A.